How common is this, really, though? It's pretty rare that someone actually converts an existing single disk setup into a RAID. It's far more common to add/remov

How common is this, really, though? It's pretty rare that someone actually converts an existing single disk setup into a RAID. It's far more common to add/remove/replace devices in an existing array. These tasks have always been fairly trivial with the mdadm tool. The most sane way to accomplish this under Linux is to create a broken mirror with the new device (device B), synchronize device A's contents to the array with dd, and then add device A to the array.